Such a method and rolling mill for making seamless pipes by means of a continuous rolling method (continuous pipe rolling method) with a continuous rolling mill, also referred to as continuous pipe rolling mill, is known for example from DE-Z Bergund Hüttenmännische Monatshefte 130 (1985), Volume 7, pages 205-211. In most cases, rolled round steel bars are used as feed material, primarily in the form of continuous casting rounds with a diameter of up to 350 mm which are brought to rolling temperature in a rotary hearth furnace in lengths of up to 5 m. Subsequently, the piercing of the solid block to form a thin-walled hollow block takes place on a piercing mill which is normally constructed as a cross-roll piercing mill. The hollow block produced in this manner is then rolled in the same heat in the continuous rolling mill over a mandrel to form a tube blank. The continuous rolling mill consists mostly of six to nine rolling stands closely juxtaposed one behind the other, offset with respect to one another for example by 90°.
Before the start of the rolling process in the rolling mill, the hollow block including the mandrel inserted in it is moved in position by an upstream mandrel manipulator referred to in the industry as a conveyor, and is then pushed into the continuous rolling mill. There, the hollow block is gripped by the rolls and rolled out on the mandrel by the reduction rolls which become smaller from roll stand to roll stand. The mandrel is fed here by the mandrel conveyor during the rolling process with controlled, semicontrolled or fully controlled mandrel speed.
In the one case, the mandrel is released shortly before the end of rolling so that the mandrel and tube blank exit the rolling mill in the rolling direction and are transferred to a stripper where the mandrel is extracted. In the second case, in which the mandrel is fed during the entire rolling process with constant speed, the tube blank is pulled off the mandrel in an extracting rolling mill downstream of the continuous rolling mill. After this, the mandrel is returned back upstream. For these methods, and also for the methods known as free-floating method (free circulating mandrel), or semifloating method (mandrel restrained during rolling and afterward circulating), and restrained method (mandrel restrained during rolling, afterward pulled back), either a high production rate, if applicable combined with a short mandrel length (semifloating), but at the same time with an nonuniform tube blank temperature requiring a reheating of the tube blanks for subsequent processing can be implemented, or a uniform tube blank temperature, but with high cycle times due to the return transport and hence a low production rate can be implemented.
From DE 28 11 801 A1, a rolling mill with a multistand continuous rolling and a multistand extracting rolling mill is known in which a pipe to be rolled is rolled by a mandrel retained before the continuous rolling mill.
From DE 31 36 381 A1 and DE 142 79 15 A1, rolling mills are known that have one continuous rolling mill and one extracting rolling mill and that, between the continuous rolling mill and the extracting rolling mill, have a holding fixture for a mandrel conveyor.